Crystal River loss of instrumentation power supply event

The transient presented in this report occurred when one of two instrumentation power supplies was lost. The PORV opened due to the loss of instrumentation power. The operators, having recently been trained on the TMI-2 accident recognized the open PORV, and closed the block valve. They continued high pressure injection according to procedures, which resulted in pressure relief through the pressurizer code safety valves. The pressurizer was eventually overfilled, and liquid was released through the safety valve. The transient also includes reactor coolant pump trip and coastdown to natural circulation and asymmetric cooldown with feedwater cooling in only one steam generator. This sequence of events provides a unique test of the capabilities of the MMS modules to simulate actual plant conditions. The plant simulated in this transient is Crystal River Unit 3, a BandW 177 fuel assembly plant. The design is nearly identical with the TMI-2 design which has been modeled for two other events. The results of this simulation include the initial state shown. The steady state results are acceptable considering the inconsistencies in between the neutron flux detectors and the heat balances on the primary and secondary. The transient results are not completely satisfactory. Work to benchmark on this transient was stopped because time and money had run out and the measured data were not complete enough to be certain of the cause of the discrepancies